The World's Biggest Sinkholes

A sinkhole occurs when an area of ground collapses, creating holes that can swallow up swimming pools, roads, buildings and people.

The United States Geological Survey describes three different categories of sinkholes based on how they are created: dissolution, cover-subsidence and cover-collapse sinkholes.

In all three, erosion of land is caused by minerals washed away by water over time.

The most dangerous type of sink hole, and the ones we usually see in the news, are cover-collapse sink holes. The erosion of land occurs underground, creating a cavity under streets, sidewalks or buildings. Eventually the ground suddenly collapses since there's nothing underneath holding it up.